Wireless sensor system and wheel support bearing assembly utilizing the same

ABSTRACT

To provide a wireless sensor system, in which an abnormal power supply in the power supply section can be ascertained, for avoiding a malfunction of the system and accomplishing a stable power supply with reduction of the consumption of a power being transmitted, the wireless sensor system includes wireless sensor units and a sensor signal receiving unit. The wireless sensor units include a sensor section for detecting a detection object, a sensor signal transmitting section for transmitting by wireless a sensor signal from the sensor section, and a power supply section having a power receiving section for receiving a driving power transmitted by wireless. In this system, a power supply monitoring section is provided for monitoring the voltage of the power supply section. The sensor signal receiving unit includes a monitor dependent power control section for regulating the power to be transmitted, depending on a monitored result of the power monitoring section.

This application claims the benefit of PCT International ApplicationNumber PCT/JP2004/003138 filed Mar. 10, 2004 and Japanese ApplicationNos. 2003-306964 and 2003-307515, filed Aug. 29, 2003, in Japan, thedisclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a wireless sensor system for wirelesslytransmitting various sensor signals, for example, those generated fromvarious sensors installed in a wheel support bearing assembly in variousmachine, equipment and automotive vehicles and also to a wheel supportbearing assembly utilizing such wireless sensor system.

BACKGROUND ART

A wireless ABS (anti-skid brake system) sensor system has beensuggested, in which sensor signals generated from a revolution sensormounted on a wheel support bearing assembly is transmitted by wirelessbetween a vehicle wheel and an automotive body to thereby eliminate theuse of harnesses. On the other hand, the Japanese Laid-open PatentPublication No. 2003-146196, published May 21, 2003, discloses thesystem in which in a wheel support bearing assembly equipped with arevolution sensor, output signals of which are transmitted by wireless,the presence or absence of an abnormality in the revolution sensor isdetermined by means of a self-diagnosing circuit and an abnormalityindication signal when generated from such circuit can be transmitted bywireless. Those suggestions require that supply of an electric power tothe revolution sensor and also to a wireless transmitting system to beprovided for by the revolution sensor that concurrently serves as anelectric power generator but supply of an electric power by wirelessfrom an outside power source is also referred to in those suggestions.

DISCLOSURE OF THE INVENTION

In the wireless sensor system in which an electric operating power issupplied through supply of the electric power by wireless, the wirelesssupply of the electric power is carried out by the utilization ofelectromagnetic waves or light waves. The wireless supply of theelectric power tends to be adversely affected by obstacles presentbetween the transmitter and the receiver and/or by a relative movementof the receiver to the transmitter, and vice versa, to such an extent asto result in failure to supply the sufficient amount of electric powerand, therefore, care must be taken in selecting where to install. Forthis reason, there is a problem in that continued supply of the largeamount of electric power as a precaution against the failure of theelectric power supply may result in increase of the electric powerconsumption of the system as a whole. Also, in the system in which theelectric power supply is carried out from the revolution sensorconcurrently serving as an electric power generator, the wireless sensorsystem may occasionally fail to operate properly as a result ofabnormality occurring in the transmission system when an abnormality isdetected. Provision of an abnormality detecting means in each of thesensor system and the transmission system will render the wirelesssensor system as a whole to be complicated in configuration.

Accordingly, an object of the present invention is to provide a wirelesssensor system of a simplified structure, in which the presence orabsence of an abnormality in electric power supply occurring in electricpower supply section for supplying an electric driving power to thesensors and the sensor signal transmitting section can be ascertainedand which is also effective to avoid an erroneous operation of thewireless sensor system resulting from an erroneous operation of thesensors and/or the sensor signal transmitting sections.

Another object of the present invention is to accomplish a stableelectric power supply, accompanied by reduction of the consumption of anelectric power being transmitted.

A further object of the present invention is to provide a wirelesssensor equipped bearing assembly, which is capable of rendering abearing assembly to be intelligent and to have a simplified wiringsystem, in which the presence or absence of an abnormality in electricpower supply to the sensors and the sensor signal transmitting sectioncan be ascertained to minimize the occurrence of an erroneous operationand the consumption of the electric power, and which makes use of asimplified in structure for minimizing those erroneous operations.

A still further object of the present invention is to obtain thefunctionality of the wireless sensor equipped bearing assembly in awheel support bearing assembly.

The wireless sensor system of the present invention includes, inreference to FIG. 1, one or a plurality of wireless sensor units (4A,4B) including a sensor section (6A, 6B) for detecting a detectionobject, a sensor signal transmitting section (9A, 9B) for transmittingby wireless a sensor signal outputted from the sensor section (6A, 6B),and an electric power supply section (10) for supplying an electricdriving power to the sensor section (6A, 6B) and the sensor signaltransmitting section (9A, 9B); and a sensor signal receiving unit (13)for receiving the sensor signal transmitted from the sensor signaltransmitting section (9A, 9B), and is characterized by comprising anelectric power supply monitoring section (7) for monitoring a voltage ofthe electric power supply section (10).

According to the present invention, the voltage of the electric powersupplied, as the electric driving power, from the electric power supplysection (10) to the sensor section (6A, 6B) and also to the sensorsignal transmitting section (9A, 9B) is monitored by the electric powersupply monitoring section (7). Accordingly, if the occurrence of anabnormality in electric power supply is indicated, any erroneousoperation of the sensor section (6A, 6B) and/or that of the wirelesssensor system can be prevented. Also, since the electric driving powerof the electric power supply section (10) is monitored, the occurrenceof an abnormality in electric power supply in the sensor section (6A,6B) and in the sensor signal transmitting section (9A, 9B) resultingfrom the failure of electric power supply can be both detected and, ascompared with the case in which separate abnormality detecting means areemployed, the structure can be simplified.

In the present invention, the electric power supply section (10)referred to above may include an electric power receiving section (8A,8B) for receiving an electric driving power transmitted by wireless froma feed power transmitting section. Wireless transmission and receipt ofthe sensor signal and the electric operating power may be carried out bythe utilization of electromagnetic waves, magnetic coupling, light andultrasonic waves or any other medium that can accomplish them bywireless.

In the case of the wireless supply of the electric power, it isnecessary to transmit a large electric power for the supply of theelectric power since as compared with the wired supply of the electricpower or a built-in electric power generator, the efficiency isrelatively low. However, if the electric power supply is monitored andthe presence of an abnormality in electric power supply and feed powersignal are indicated to the transmitting side, the electric power to betransmitted by wireless for the wireless electric power supply can becontrolled so that the stabilized electric power supply can beaccomplished while reducing the consumption of the electric transmittingpower.

By way of example, where the electric power receiving section (8A, 8B)referred to above is employed, the electric power supply monitoringsection (7) may be designed to allow a monitored result information tobe transmitted from the sensor signal transmitting section (9A, 9B). Insuch case, a monitor dependent control section (14) may be employed forregulating an electric power to be transmitted from the feed powertransmitting section, in dependence on a monitored result informationfrom the electric power supply monitoring section (7).

Considering that the monitored result information of the voltage of theelectric power to be supplied can be transmitted, the receiving side ofthe sensor signal can recognize the monitored result information and,therefore, a countermeasure appropriate to the result of the monitoringcan be taken. In particular, where the wireless supply of the electricpower takes place from the feed power transmitting section, theprovision of the monitor dependent control section (14) is effective toallow the electric power to be transmitted for the wireless electricpower supply to be controlled in dependence on the monitored resultinformation on the voltage of the electric power to be supplied.Accordingly, there is no need to transmit the large electric power atall times and the electric power consumption of the wireless sensorsystem can therefore be reduced.

The feed power transmitting section (12) referred to above may beprovided in a sensor signal receiving unit (5) including the sensorsignal receiving section (13). Where the monitor dependent controlsection (14) is employed, this monitor dependent control section (14) isalso provided in the sensor signal receiving unit (5). Although thesensor signal receiving section (13) and the feed power transmittingmeans (12) may be arranged in spaced relation to each other, theprovision of the both in the sensor signal receiving unit (5) iseffective to simplify the structure of the wireless sensor system.

The electric power supply monitoring section (7) may be of a typecapable of monitoring the voltage after the electric power received bythe electric power receiving section (12) has been converted into adirect current. If the voltage after the conversion into the directcurrent is monitored, the monitoring can be accomplished easily and theelectric power supply monitoring section (7) can have a simplifiedstructure.

The sensor signal transmitting section (9A, 9B) may be of a type capableof transmitting a predetermined normal indication signal when thevoltage monitored by the electric power supply monitoring section (7) isequal to or higher than, or exceeds, a predetermined threshold value,and interrupts the transmission of the normal indication signal whensuch voltage is lower than, or equal to or lower than, the predeterminedthreshold value. Also, arrangement may be made that a predeterminedabnormality indication signal can be transmitted during theinterruption. The predetermined normal indication signal may be anelectric power voltage signal and may be in the form of, for example,the sensor signal superimposed with the electric power voltage signal.In this way, when the transmission of the normal indication signal isinterrupted when the voltage is lower than the threshold value, or thepredetermined abnormality indication signal is further transmitted, thepresence or absence of an abnormality can easily be recognized on thereceiving side of the sensor signal. Also, as compared with the use of atransmitting and receiving means for transmitting and receiving correctand error signals separate from the sensor signal transmitting section(9A, 9B), the structure can be simplified.

In the present invention, the sensor section (6A, 6B) referred to abovemay include a revolution sensor (6Ab) having an electric powergenerating function and the electric power supply section (10) mayutilize an electric power generated by the revolution sensor (6Ab). Insuch case, the wireless supplied electric power and the generatedelectric power can be concurrently employed.

Even where the electric power generated by the revolution sensor (6Ab)is utilized, the provision of the electric power supply monitoringsection (7) for monitoring the voltage of the electric power supplysection (10), which supplies the electric driving power to the sensorsection (6A, 6B) and the sensor signal transmitting section (9A, 9B), iseffective to allow the abnormality occurring in the supply of theelectric power to the sensor section (6A, 6B) and to the sensor signaltransmitting section (9A, 9B) resulting from an electric power supplyfailure to be detected and, therefore, as compared with the use ofseparate abnormality detecting means, the system can be simplified instructure.

In the present invention, the sensor section (6A, 6B) may include atleast one of a vibration sensor, a temperature sensor, a load sensor, atorque sensor, and a preload sensor for detecting a preload of a bearingassembly.

In the wireless sensor system of the present invention as describedabove, the sensor section (6A to 6E) may be provided in a plural number.

Where the plural sensor sections (6A to 6E) are employed, each of thesensor signal receiving section (13) may be of a type operable toreceive respective sensor signals from those plural sensor sections (6Ato 6E), which are transmitted from the sensor signal transmittingsections (9A, 9B, 9), respectively, and the feed power transmittingsection (12) may be provided in the sensor signal receiving unit (5, 5A)including the sensor signal receiving section (13). In the case of thisconstruction, receipt of the sensor signals from the plural sensorsections (6A to 6E) and wireless transmission of the feed power can becarried out commonly by the sensor signal transmitting unit (5, 5A) and,therefore, the wireless sensor system as a whole can be simplified instructure.

BRIEF DESCRIPTION OF THE DRAWINGS

In any event, the present invention will become more clearly understoodfrom the following description of preferred embodiments thereof, whentaken in conjunction with the accompanying drawings. However, theembodiments and the drawings are given only for the purpose ofillustration and explanation, and are not to be taken as limiting thescope of the present invention in any way whatsoever, which scope is tobe determined by the appended claims. In the accompanying drawings, likereference numerals are used to denote like parts throughout the severalviews, and:

FIG. 1 is a circuit section block diagram showing a general structure ofa wireless sensor system according to a first preferred embodiment ofthe present invention;

FIG. 2 is a circuit section diagram of the wireless sensor system shownin FIG. 1, showing a specific example of structure thereof;

FIG. 3 is a circuit section diagram of a sensor signal receiving unitforming a part of the wireless sensor system according to a secondpreferred embodiment of the present invention;

FIG. 4 is a longitudinal sectional view of the machine setup equippedwith and operatively linked with each other through the wireless sensorsystem according to the first preferred embodiment of the presentinvention;

FIG. 5 is a longitudinal sectional view of the different machine setupequipped with and operatively linked with each other through thewireless sensor system according to the first embodiment of the presentinvention;

FIG. 6 is a longitudinal sectional view of a bearing assembly equippedwith a component of the wireless sensor system according to the firstembodiment of the present invention;

FIG. 7 is a longitudinal sectional view of a wheel support bearingassembly equipped with a component of the wireless sensor systemaccording to the first embodiment of the present invention;

FIG. 8 is a longitudinal sectional view of a different wheel supportbearing assembly equipped with the component of the wireless sensorsystem according to the first embodiment of the present invention;

FIG. 9A is a side view, with a portion cut out, of a torque sensordefining a sensor section forming a part of the wireless sensor system;

FIG. 9B is a transverse sectional view of a magnetostrictive member ofthe sensor section shown in FIG. 9A;

FIG. 10 is a circuit section diagram showing the general structure ofthe wireless sensor system according to a third preferred embodiment ofthe present invention;

FIG. 11 is a longitudinal sectional view of the wheel support bearingassembly to which the wireless sensor system shown in FIG. 10 isapplied;

FIG. 12 is a longitudinal sectional view of the different wheel supportbearing assembly to which the wireless sensor system shown in FIG. 10 isapplied;

FIG. 13 is a longitudinal sectional view showing the different bearingassembly to which the wireless sensor system according to the firstembodiment of the present invention is applied;

FIG. 14 is a longitudinal sectional view showing the further wheelsupport bearing assembly to which the wireless sensor system accordingto the first embodiment of the present invention is applied;

FIG. 15 is a longitudinal sectional view showing the still further wheelsupport bearing assembly to which the wireless sensor system accordingto the first embodiment of the present invention is applied;

FIG. 16 is a circuit section diagram of a wireless sensor unit of thewireless sensor system according to a fourth preferred embodiment of thepresent invention; and

FIG. 17 is a longitudinal sectional view of the wheel support bearingassembly to which the wireless sensor system according to the fourthembodiment of the present invention is applied.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A wireless sensor system according to a first preferred embodiment ofthe present invention will be described with particular reference toFIG. 1. This wireless sensor system includes a plurality of wirelesssensor unit 4A and 4B, and a sensor signal receiving unit 5 forsupplying by wireless an electric power to each of those wireless sensorunits 4A and 4B and also for receiving by wireless sensor signals fromthe respective wireless sensor units 4A and 4B. The number of thewireless sensor units employed is not specifically limited to aparticular number and one or more than two wireless sensor units may beemployed, it being however to be noted that the use of the two wirelesssensor units is shown in FIG. 1.

Each of the wireless sensor units 4A and 4B includes a sensor section 6Aor 6B and a transmitting and receiving section 7A or 7B. Each of thesensor sections 6A and 6B defines means for detecting an object to bedetected or detection object and at least one of a vibration sensor, atemperature sensor, a load sensor, a torque sensor and a preload sensorfor detecting a preload on a bearing assembly is included in thoseplural sensor sections 6A and 6B. The remaining sensor sections 6A and6B may be a revolution sensor. A sensor defining the revolution sensormay be of a Hall type sensor or a magnetic reluctance type sensor. Eachof the transmitting and receiving sections 7A and 7B includes anelectric power receiving section 8A or 8B and a sensor signaltransmitting section 9A or 9B.

In the embodiment shown in FIG. 1, electric power supply sections 10 forsupplying an electric driving power to the sensor sections 6A and 6B andthe sensor signal transmitters 9A and 9B, and electric power supplymonitoring sections 7 are additionally provided . The electric powersupply sections 10 and the electric power supply monitoring sections 7will be described later.

As shown in FIG. 2, each of the electric power receiving sections 8A and8B defines means for acquiring from an electromagnetic wave of apredetermined power supply frequency f1, an electric operating powerthrough a respective tuning circuit 10A or 10B and a respectivedetecting and rectifying circuit 11A or 11B. The acquired electricoperating power is utilized to drive the sensor sections 6A and 6B andthe sensor signal transmitting sections 9A and 9B. Each of the electricpower receiving sections 8A and 8B includes the tuning circuit 10A or10B, made up of an antenna 22 and an LC circuit 23, and the detectingand rectifying circuit 11A or 11B made up of a diode 24 and a capacitor25.

Each of the sensor signal transmitting sections 9A and 9B defines meansfor transmitting a signal, detected by the corresponding sensor section6A or 6B, in the form of an electromagnetic wave sensor signal of aunique frequency f2 or f3 that is different from the power supplyfrequency f1. Each sensor signal transmitting section 9A or 9B includesan antenna 19, an LC circuit 20 and a semiconductor switching element21.

The sensor signal receiving unit 5 includes a feed power transmittingsection 12 which transmits an electromagnetic wave of the power supplyfrequency f1 and a sensor signal receiving section 13 capable ofreceiving wireless sensor signals of the respective natural frequenciesf2 and f3 transmitted from the plural wireless sensor units 4A and 4B.The feed power transmitting section 12 in turn includes a high frequencyoscillating section 26 and a transmitting section 27, which includes anantenna 28, an LC circuit 29 and a semiconductor switching element 30.The sensor signal receiving section 13 includes a plurality of, (forexample, two, in the illustrated embodiment), receiving circuits 13 aassociated respectively with the wireless sensor units 4A and 4B. Eachof the receiving circuits 13 a is a receiving circuit for receiving asingle frequency corresponding to each of the natural frequencies f2 andf3 transmitted from the respective wireless sensor units 4A and 4B andincludes a tuning circuit 37 and a detecting section 38. Each tuningcircuit 37 in turn includes an antenna 39 and an LC circuit 40.

According to the wireless sensor system of the above describedconstruction, each of the wireless sensor units 4A and 4B is supplied bywireless with the electric operating power, neither a battery nor anelectric generator is needed as a sensor operating electric power sourceand, therefore, the sensor system can be assembled compact in size andlightweight. Since no replacement of any battery is needed, themaintenance is easy to accomplish. Moreover, as the detection object,vibration, temperature, load, torque or preload on the bearing assemblycan be detected. Also, since arrangement has been made that wirelessreception of the wireless sensor signals and wireless supply of theelectric power can be made from the common sensor signal receiving unit5 to the plural wireless sensor units 4A and 4B, the wireless sensorsystem as a whole can have a simplified structure.

FIG. 3 illustrates the structure of the sensor signal receiving unit 5Aaccording to a second preferred embodiment of the present invention.This embodiment is such that in the first embodiment shown in FIG. 2,the sensor signal receiving unit 5A is so structured as shown therein.The same wireless sensor units as in the first embodiments are employed.In this embodiment, the sensor signal receiving section 13A of thesensor signal receiving unit 5A includes a plurality of tuning circuits37A and 37B of a single frequency corresponding to each of the naturalfrequencies f2 and f3 transmitted from the respective wireless sensorunits 4A and 4B (FIG. 2) and a single switching detector section 41 fordetecting respective outputs from the tuning circuits 37A and 37B on atime sharing basis. The switching detector section 41 is made up of adetector 42 and a selector 43 for selecting one of the tuning circuits37A and 37B on a time sharing basis and then connecting it to thedetector 42. Other structural features than those mentioned above areidentical with those employed in the sensor signal receiving unit 5 inthe previously described first embodiment.

In the case of this embodiment, when the selector 43 of the switchingdetector section 41 is held in position to connect the tuning circuit37A with the detector 42, the signal of the frequency f2 fed from thewireless sensor unit 4A, employed to detect the number of revolutions,and then received by the tuning circuit 37A is detected by the detector42. On the other hand, when the selector 43 of the switching detectorsection 41 is held in position to connect the tuning circuit 37B withthe detector 42, the signal of the frequency f3 fed from the wirelesssensor unit 4B and then received by the tuning circuit 37B is detectedby the detector 42.

In the case of this embodiment, the electromagnetic waves of the naturalfrequencies f2 and f3 transmitted from the plurality of, (two, in theillustrated embodiment), the wireless sensor units 4A and 4B,respectively, can be separately detected selectively one at a time bythe single detector 42 in the sensor signal receiving unit 5A and,therefore, the structure of the sensor signal receiving unit 5A can besimplified even where the number of the wireless sensor units is large.

It is to be noted that in the embodiment shown in FIG. 3, instead of theuse of the plural tuning circuits 37A and 37B, a single tuning circuitcapable of changing a tuning frequency in correspondence with the uniquefrequency transmitted from each of the wireless sensor units 4A and 4B(FIG. 2) may be employed. In such case, the sensor signal receivingsection 13A has to be so configured that the unique frequency of thevariable tuning circuit be selected on a time sharing basis by aselector and be then detected by the detector 42.

In the next place, application of the wireless sensor system accordingto the first embodiment to the machine setup will be described in detailwith particular reference to FIG. 4. In this example, the machine setup53 includes a plurality of rolling bearing assemblies 51 and 52, whichare equipped with the respective wireless sensor units 4A and 4B shownand described in connection with any one of the embodiments of FIGS. 1and 2. The machine setup 53 is in the form of, for example, a conveyorline including, for example, roller conveyors or belt conveyors, inwhich rotary shafts 59, each forming a shaft for transport rollers orbelt drive rollers, are rotatably supported respectively by the rollingbearing assemblies 51 and 52. Each of the rolling bearing assemblies 51and 52 is of a type including a circular row of rolling elements 56interposed between an inner race 54 and an outer race 55 and providedwith a sealing member 58 and is in the form of a deep groove ballbearing assembly or the like. The rolling elements 56 in each of therolling bearing assemblies 51 and 52 are retained by a retainer 57.

The wireless sensor unit 4A mounted in the rolling bearing assembly 51is used for the detection of the number of revolutions, which includesthe sensor section 6A made up of a magnetic encoder 17, mounted on theinner race 54, and a magnetic sensor 18 such as, for example, a Hallsensor or MR sensor mounted on the outer race 55 in face-to-facerelation with the magnetic encoder 17. The wireless sensor unit 4Bmounted in the other rolling bearing assembly 52 includes the sensorsection 6B used to detect a detection object of the bearing assembly 52other than the number of revolutions, for example, temperature orvibration. The sensor section 6B is mounted on one of the inner race 54and the outer race 55, which serves as a stationary race member (theouter race 55 in the illustrated embodiment). The sensor section 6B maybe a sensor for detecting a load, torque or preload on the bearingassembly other than that described above.

Also, instead of the sensor section 6A in the rolling bearing assembly51 being used as a revolution sensor to detect the number ofrevolutions, any of the sensor sections 6A and 6B may be used as one ofa vibration sensor, a temperature sensor, a preload sensor, a torquesensor or a preload sensor for the detection of a preload on the bearingassemblies 51 and 52 as shown in FIG. 5.

In the machine setup 53, the sensor signal receiving unit 5 is disposedat any suitable site convenient to receive sensor signals from each ofthe wireless sensor units 4A and 4B provided in the respective bearingassemblies 51 and 52, and also to transmit the electric operating powerto each of the wireless sensor units 4A and 4B. In this illustratedembodiment, the construction is identical with that according to any oneof the embodiments shown respectively in FIGS. 1 and 2, unless otherwisespecified.

In the case of this construction, in the plural rolling bearingassemblies 51 and 52 in the machine setup 53, respective sensor signalsdetected through the wireless sensor units 4A and 4B can be received bythe common sensor signal receiving unit 5 and, also, the electric powercan be supplied from the common sensor signal receiving unit 5 to bothof the wireless sensor units 4A and 4B.

In the embodiment shown therein, although reference has been made to theuse of the two wireless sensor units 4A and 4B, each wireless sensorunit may be disposed in three or more rolling bearing assemblies in themachine setup 53, with the common sensor signal receiving unit 5 allowedto receive the respective sensor signals and to supply the electricpower by wireless.

FIG. 6 illustrates an example of a bearing assembly equipped with thewireless sensor of a kind employing a preload sensor as any one of thesensor sections 6A or 6B. This bearing assembly 61 is in the form of arolling bearing assembly including a circular row of rolling elements 66interposed between an inner race 64 and an outer race 65 and ispreloaded by a preloading means 70. The rolling elements 66 are retainedby a retainer 67. This bearing assembly 61 is in the form of a dual rowtapered roller bearing assembly having the inner race 64 mounted on ashaft 69. The preloading means 70 urges the inner race 64, situatedbetween an inner race spacer 63 and a shoulder 69 a of the shaft 69, ina direction axially of the inner race 64 by means of a nut 62threadingly mounted on an externally threaded portion of the shaft 69,to thereby apply a preload to the bearing assembly 61. The sensorsection 6A in the form of a preload sensor for detecting the preload onthe bearing assembly is mounted on the inner race spacer 63. This sensorsection 6A is the one provided in the wireless sensor unit 4A in thewireless sensor system in, for example, the embodiment shown in FIG. 1.The preload sensor referred to above includes a load sensor utilizing,for example, a piezoelectric element or a load sensor of amagnetostrictive type and is operable to detect an axial load actingaxially on the inner race spacer 63.

It is to be noted that although in this embodiment the inner race 64serves as a rotating member with the wireless sensor unit 4A mounted onthe rotatable spacer 63, the inner race 64 may serve as a stationarymember. Also, the wireless sensor unit 4A and its sensor section 6A maybe mounted on a spacer (not shown) on the side of the outer race 65.Yet, the sensor section 6A may be mounted on a spacer positioned betweenthe inner races.

Another application of the wireless sensor system according to thisembodiment to an automotive vehicle will now be described withparticular reference to FIG. 7. The wheel support bearing assembly 33includes dual rows of rolling elements 3 interposed between an outermember 1, serving as a stationary member, and an inner member 2 servingas a rotatable member. The outer member 1 is supported by a suspension,protruding downwardly from an vehicle body 34, through a knuckle (notshown). The inner member 2 is made up of a hub axle 2A and an inner racesegment 2B mounted coaxially on one end of the hub axle 2A, withrespective raceways defined in the hub axle 2A and the inner racesegment 2B. The outer member 1 is of one-piece construction and hasraceways defined therein in alignment of the raceways in the innermember 2. The hub axle 2A is coupled with a shaft portion provided in anouter race 15 a of a constant velocity universal joint 15, with theinner member 2 and the outer race 15 a of the constant velocityuniversal joint consequently coupled together. It is to be noted thatthis wheel support bearing assembly 33 is of a third generation type.

The plural wireless sensor units 4A and 4B are mounted on the outermember 1 of this wheel support bearing assembly 33. For example, thewireless sensor unit 4A including the sensor section 6A operable todetect the number of revolutions of a vehicle wheel 31 is disposedwithin one end of an annular bearing space delimited between the outermember 1 and the inner member 2. The other wireless sensor unit 4Bmounted on the outer member 1 includes the sensor section 6B that isrendered to be a vibration sensor or a temperature sensor. The sensorsection 6B may be, other than that described above, a load sensor, atorque sensor or a preload sensor. The sensor signal receiving unit 5for supplying an electric power by wireless to each of the wirelesssensor units 4A and 4B and also for receiving respective sensor signalsfrom the wireless sensor units 4A and 4B is accommodated within, forexample, a tire housing 34 a of the vehicle body 34. The wireless sensorunits 4A and 4B are of a structure identical with those shown in anddescribed with reference of any one of FIGS. 1 and 2. The sensor signalreceiving unit 5 may be either the one shown in and described withreference to FIG. 2 or the one shown in and described with reference toFIG. 3.

The sensor section 6A of the wireless sensor unit 4A, which is used forthe detection of the number of revolutions, includes a magnetic encoder17, mounted on the inner member 2, and a magnetic sensor 18 mounted onthe outer member 1 in face-to-face relation with the magnetic encoder17. The magnetic encoder 17 is secured to a slinger forming a part of asealing structure mounted on the inner member 2. The magnetic encoder 17includes a multipolar magnet having a plurality of magnetic poles N andS alternating in a direction circumferentially thereof. On the otherhand, this magnetic sensor 18 is in the form of a magnetic sensor suchas, for example, a Hall sensor or an MR sensor and is operable to detecta change in magnetic polarity of the magnetic encoder 17 resulting fromrevolution of the vehicle wheel 31 and then output, as the sensorsignal, an incremental pulse signal indicative of such change inmagnetic polarity.

The sensor section 6B of the other wireless sensor unit 4B includes atemperature sensor in the form of, for example, a thermocouple or avibration sensor of a type utilizing a piezoelectric element or thelike.

Hereinafter, the operation will be described. Power supplyelectromagnetic waves transmitted from the feed power transmittingsection 12 (FIG. 1) of the sensor signal receiving unit 5 mounted on thevehicle body 34 are detected and rectified by the electric powerreceiving section 8A and 8B (FIG. 1) of the wireless sensor units 4A and4B to thereby provide the wireless sensor units 4A and 4B with electricdriving powers.

In the wireless sensor units 4A and 4B mounted on the wheel supportbearing assembly 33, the number of revolutions of the vehicle wheel isdetected by the sensor section 6A and, on the other hand, thetemperature or vibration of the wheel support bearing assembly, or theload, torque or preload acting on the wheel support bearing assembly isdetected by the sensor section 6B. The sensor signals so detected aretransmitted by wireless to the sensor signal receiving unit 5.Specifically, the sensor signals so detected are transmitted by thesensor signal transmitting section 9A (FIG. 1) by wireless in the formof a carrier wave comprised of electromagnetic waves of the frequencyf2. The electromagnetic waves are then received and detected by one ofthe receiving circuits in the sensor signal receiving section 13(FIG. 1) of the sensor signal receiving unit 5, which has a frequencycorresponding thereto and which subsequently outputs a detection signalindicative of the number of revolutions of the vehicle wheel, a signalindicative of the temperature, vibration or load, or a signal indicativeof the load, torque or preload. The number of revolutions of the vehiclewheel is utilized for the control of an ABS system, and the detectionsignal indicative of the temperature, vibration or preload is utilizedfor the detection of the presence or absence of any abnormality in thewheel support bearing assembly 33 and/or for the maintenance of thestatus. On the other hand, the detection signal indicative of the loador torque is utilized for the control of the running attitude of theautomotive vehicle.

As hereinabove described, since in this wireless sensor system, theelectric power is supplied by wireless in the form of theelectromagnetic wave from the sensor signal receiving unit 5, mounted onthe vehicle body 34, to each of the wireless sensor units 4A and 4B and,also, the sensor signals transmitted in the form of the electromagneticwaves from the wireless sensor units 4A and 4B are received by thesensor signal receiving unit 5, there is no problem associated withrun-out of the battery that is encountered in the conventional exampleutilizing the battery as a power source. Also, each of the detectedsensor signals can be assuredly transmitted in the form of a wirelesssignal and each of the sensor sections 6A and 6B of the respectivewireless sensor units 4A and 4B can be compactly and inexpensivelymanufactured. Since no battery replacement is required, the maintenancecan be accomplished easily.

Also, unlike a self-generation type, operation of the sensor sections 6Aand 6B and transmission of the sensor signals can be performed evenduring rotation of the vehicle wheel at an extremely low speedapproximating to a halt. It is to be noted that the wireless sensorunits 4A and 4B may be arranged within the bearing assembly that issealed with the sealing member. Also, only the sensor sections 6A and 6Bmay be inserted inside the bearing assembly.

FIG. 8 illustrates another example of the wheel support bearing assembly33. In this example, the sensor section 6A provided in the wirelesssensor unit 4A is employed as a torque sensor. The sensor section 6Aserving as the torque sensor includes a to-be-detected member 71,mounted externally on the inner member 2 and made of a magnetostrictivematerial, and a torque detecting member 72 mounted on the outer member 2in correspondence with the to-be-detected member 71. The torquedetecting member 72 is operable to detect a change in magneticcharacteristic of the to-be-detected member 71 to thereby detect thetorque acting on a drive shaft fitted to the inner member 2. As themagnetostrictive material for the to-be-detected member 71, an alloy ofiron and aluminum or the like is suitably employed. The torque detectingmember 72 is in the form of a coil fitted to the outer member 1 so as toencircle the to-be-detected member 71. The to-be-detected member 71includes, for example, as shown in FIG. 9, a cylindrical body 73, madeof a magnetostrictive material, and circumferentially juxtaposed tworows of inclined grooves 74 that are inclined at respectivepredetermined angles θ1 and θ2 relative to the axial direction. Therespective angles θ1 and θ2 of inclination of the inclined grooves 74 ofthe two rows lie in a sense opposite to each other. The provision of theinclined grooves 74 is effective to increase the sensitivity and thedesign, in which the respective angles θ1 and θ2 of inclination arechosen to lie in a sense opposite to each other, is effective to providenot only an indication of the magnitude of the torsional torque actingon the shaft, but also an indication of the direction thereof In suchcase, an output from the coil of the torque detecting member 72 isprocessed by a detecting circuit (not shown) and is then transmitted bywireless from the sensor signal transmitting section 9A (FIG. 1) of thewireless sensor unit 4A.

It is to be noted that although the wireless sensor unit 4A employed inthe example shown in FIG. 8 is the one employed in the wireless sensorsystem in, for example, any one of the embodiments shown in FIGS. 1 and2, the other wireless sensor unit 4B (not shown in FIG. 8) may bearranged in this wheel support bearing assembly 33 with the sensorsection 6B thereof used as a sensor for detecting the detection objectsuch as the vibration, temperature, load or preload.

FIG. 10 illustrates a third preferred embodiment of the presentinvention. The wireless sensor system according to this embodiment makesuse of the only wireless sensor unit 4 and this only wireless sensorunit 4 is provided with a plurality of sensor sections 6C to 6E. Thewireless sensor unit 4 includes, in addition to the plural sensorsections 6C to 6E, a sensor signal transmitting section 9 and anelectric power receiving section 8. The sensor signal transmittingsection 9 is used to transmit respective sensor signals of the pluralsensor sections 6C to 6E. The respective outputs from those pluralsensor sections 6C to 6E are processed by a signal coordinating section60 so as to be capable of being transmitted from the sensor signaltransmitting section 9. This signal coordinating section 60 may be ofany suitable circuit design, provided that the respective sensor signalsfrom the sensor sections 6C to 6E can be processed so as to bediscriminately received by the receiving side and may, for example, beso designed that the respective sensor signals from the sensor sections6C to 6E can be supplied to the sensor signal transmitting section 9 ona time-shared basis. Alternatively, the signal coordinating section 60may be of a type capable of superimposing the respective sensor signalsfrom the sensor sections 6C to 6E. The signal coordinating section 60may be either incorporated in the sensor signal transmitting section 9as a part thereof or separate from the sensor signal transmittingsection 9. The electric power receiving section 8 is operable to supplyan electric power, received thereby, to the sensor sections 6C to 6E,the sensor signal transmitting section 9 and the signal coordinatingsection 60. The sensor signal transmitting section 9, the electric powerreceiving section 8 and the signal coordinating section 60 altogetherconstitute a sensor signal transmitting section 7.

The sensor signal receiving unit 5 includes a sensor signal receivingsection 13 for receiving the sensor signal, transmitted by wireless fromthe sensor signal transmitting section 9 of the wireless sensor unit 4,and an feed power transmitting section 12 for transmitting an electricpower by wireless to the electric power receiving section 8 of thewireless sensor unit 4. The sensor signal receiving section 13 is of atype capable of discriminately receiving the respective sensor signals,outputted from the sensor sections 6C to 6E and transmitted through thesensor signal transmitting section 9 of the wireless sensor unit 4, independence on a processing scheme of the signal coordinating section 60.Transmission of the signals between the sensor signal transmittingsection 9 and the sensor signal receiving section 13 and transmission ofthe electric power between the feed power transmitting section 12 andthe electric power receiving section 8 are carried out by wireless bymeans of, for example, electromagnetic waves.

The sensor sections 6C to 6E may be utilized either to detect the samedetection objects (for example, the temperatures) or to detect differentdetection objects, for example, the number of revolutions, thetemperature and the vibration.

It is also to be noted that one of the wireless sensor units 4A and 4Bemployed in the first embodiment as shown in FIG. 1 may be of a designincluding the plural sensor sections 6C to 6E as shown in FIG. 10. Insuch case, the use is preferred of the signal coordinating section 60.

FIG. 11 illustrates an application of the wireless sensor systemaccording to the third embodiment shown in and described with referenceto FIG. 10 to the wheel support bearing assembly 33, in which thewireless sensor unit 4 is mounted on the outer member 1. In thisexample, the plural sensor sections 6C to 6E are used to detect thenumber of revolutions, the temperature and the vibration, respectively.As the sensor sections 6D and 6E, a preload sensor, a load sensor and atorque sensor may be provided in place of the above.

The sensor section 6C serving as a revolution sensor includes a magneticencoder 17 containing a multipolar magnet mounted externally on theinner member 2 and a magnetic sensor 18 in the form of, for example, aHall sensor or an MR sensor mounted internally on the outer member 1 inface-to-face relation with the magnetic encoder 17. The transmitting andreceiving unit 7 is mounted externally on the outer member 1. Thistransmitting and receiving unit 7 has circuit elements accommodatedwithin a box and is electrically connected with the sensor sections 6Cto 6E by means of wiring (not shown).

The wheel support bearing assembly 33 shown therein is of a fourthgeneration type, in which the inner member 2 is made up of a hub axle 2Aand an outer race 15 a of the constant velocity universal joint 15 andrespective raceways on the inner member 2 for the dual rows of therolling elements are defined in the hub axle 2A and the outer race 15 aof the constant velocity universal joint 15, respectively. Otherstructural features of the wheel support bearing assembly 33 than thosedescribed above are identical with those of the wheel support bearingassembly 33 of the third generation type shown in and described withreference to FIG. 7. It is, however, to be noted that in the exampleshown in FIG. 11, the wheel support bearing assembly 33 may be renderedto be of a third generation type such as shown in, for example, FIG. 7.

In the case of this construction, mounting of the only wireless sensorunit 4 on the wheel support bearing assembly 33 is sufficient toaccomplish the detection of the number of revolutions of the vehiclewheel, the temperature and the vibration. Also, the wireless sensor unit4 can be supplied an electric power by wireless and the wiring systemcan therefore be simplified.

FIG. 12 illustrates an another application of the wireless sensor systemaccording to the embodiment shown in FIG. 10 to the wheel supportbearing assembly 33. In this example, the plural sensor sections 6C and6D of the wireless sensor unit 4 are employed in the form of sensorscapable of detecting the same detection objects and, hence, in the formof load sensors. The sensor sections 6C and 6D forming the load sensorsare provided in the neighborhood of respective bolt insertion holes 81defined in a flange 1 a integrated with the outer member 1. The boltinsertion holes 81 are those through which associated bolts 83 requiredto secure the outer member 1 to the knuckle 82 are inserted. The pluralsensor sections 6C and 6D are disposed in the corresponding boltinsertion holes 81 at respective location spaced up and down or left andright with respect to, for example, the longitudinal axis of the bearingassembly. The sensor sections 6C and 6D each forming the load sensor areof a type utilizing a magnetostrictive element or a piezoelectricelement as a load sensing element having an electric characteristic thatvaries in dependence on the load.

The sensor sections 6C and 6D are connected by wiring (not shown) withthe transmitting and receiving unit 7 mounted externally on the outermember. The transmitting and receiving unit 7 has circuit elementsaccommodated within a box as is the case with that describedhereinabove.

It is to be noted that although in FIG. 12, reference has been made tothe use of the two sensor sections 6C and 6D, a number of sensorsections equal to the number of bolt insertion holes 81 may be employed.Also, the sensor signal receiving unit 5, although not shown in FIG. 12,is disposed inside a tire housing in a manner similar to that describedin connection with the example of FIG. 7.

In the case of this construction, the sensor signals, or detected loadsignals, indicative of the loads detected respectively by the sensorsections 6C and 6D can be transmitted from the sensor signaltransmitting section 9 (FIG. 1) of the wireless sensor unit 4 and aresubsequently received by the sensor signal receiving section 13 (FIG. 1)of the sensor signal receiving unit 5 (FIG. 7). In reference to thevalues of the loads at the associated bolt insertion holes, which havebeen so received, the magnitude of the load acting on the outer member 1of the wheel support bearing assembly 33 can be detected and, since theplural sensor sections 6C and 6D are disposed having been spaced adistance from each other, the inclination of the direction in which theload acts can also be detected. Accordingly, the status of load on thevehicle wheel during run of the automotive vehicle along an inclinedroad surface or during curving of the automotive vehicle can be detectedand, hence, the respective signals from the plural load sensors can beused as information required to control, for example, the attitude ofthe automotive vehicle. Also, the electric operating power necessary toelectrically power the sensor sections 6C and 6D, which forms the loadsensors, and the sensor signal transmitting section 9 (FIG. 1) can besupplied by wireless in a manner similar to that in any one of theforegoing embodiments, thereby eliminating the necessity of the wiringsystem.

It is to be noted that although in any one of the foregoing embodiments,reference has been made to the use of the only sensor signal receivingunit 5, a plurality of sensor signal receiving units 5 may be employed.Where the plural sensor signal receiving units are employed, each ofthose sensor signal receiving units 5 may be so designed as to receivethe sensor signals from the sensor signal transmitting sections of thesame wireless sensor unit or to receive the sensor signals from thesensor signal transmitting sections of the different wireless sensorunits. Also, the sensor signal receiving section and the feed powertransmitting section may not be necessarily provided in the same sensorsignal receiving unit 5, but may be disposed having been spaced fromeach other. Yet, reception of the sensor signals may be carried out bymeans of separate sensor signal receivers and the electric power may besupplied by wireless to the plural wireless sensor units from the samefeed power transmitting section 12.

Also, although in any one of the foregoing embodiments, the wirelesstransmission and reception have been described as performed usingelectromagnetic waves, the present invention is satisfactorily providedthat both of the sensor signals and the electric operating power can betransmitted or received by wireless and, accordingly, transmission andreception may be carried out by the use of electromagnetic coupling,optical beams and/or ultrasonic waves.

The electric power supply section 10 of each of the wireless sensorunits 4A and 4B shown in FIG. 1 includes an electric power receivingsection 8A or 8B for receiving a corresponding electric driving power,transmitted by wireless, and an electric power supply circuit 11 forsupplying the electric power so received to the sensor section 6A or 6Band the associated sensor signal transmitting section 9A or 9B. Whereeach electric power receiving section 8A and 8B is of a type in whichsupply of the electric power by wireless is carried out by theutilization of electromagnetic wave, it is made up of a tuning circuitor the like. In such case, the electric power supply circuit 11 is madeup of a detecting and rectifying circuit or the like. The electric powersupply circuit 11 may be of a type provided with a secondary battery orcapacitor for accumulating the received electric power and a chargingcircuit therefore.

The sensor signal receiving unit 5 includes a sensor signal receivingsection 13 for discriminately receiving the sensor signals, transmittedby wireless from the respective sensor signal transmitting sections 9Aand 9B of the wireless sensor units 4A and 4B, and an feed powertransmitting section 12 for transmitting an electric power by wirelessto the respective electric power receiving sections 8A and 8B of thewireless sensor units 4A and 4B.

Transmission and reception between the sensor signal transmittingsections 9A and 9B and the sensor signal receiving section 13, andtransmission and reception between the feed power transmitting section12 and the electric power receiving sections 8A and 8B may be carriedout by the use of electromagnetic waves, light waves, infrared beams,ultrasonic waves or magnetic coupling.

Each of the sensor signals transmitted by wireless has a frequencydifferent from that of the feed electric power and, also, the pluralsensor signals have their own frequencies distinct from each other. Inthis example, the frequency of the feed electric power is designated byf1 and the respective frequencies of the sensor signals are designatedby f2 and f3.

Each of the electric power supply monitoring sections 7 is operable tomonitor the electric power supply by measuring the value of the voltageof the electric power to be supplied to the corresponding sensor section6A or 6B and the corresponding sensor signal transmitting section 9A or9B. The measurement of this electric power voltage is carried outsubject to the voltage after the received electric power has beenconverted into a direct current power. The respective electric powersupply monitoring section 7 transmits a predetermined normal indicationsignal, superimposed on the sensor signal, to the associated sensorsignal transmitting section 9A or 9B when the voltage of the electricpower to be supplied is equal to or higher than a predeterminedthreshold value, and interrupts the transmission of the normalindication signal when such voltage is lower than the threshold value.In the event that the transmission of the normal indication signal isinterrupted, the presence of an abnormality in the electric power to besupplied can be determined on the receiving side. It is to be noted thatsuperimposition and interruption of the normal indication signalreferred to above may be switched over depending on whether the voltageexceeds the threshold value or it is equal to or lower than thethreshold value. In either case, the threshold value referred to aboveis set to a value higher than the lowest voltage at which the respectivesensor section 6A or 6B and the corresponding sensor signal transmittingsection 9A or 9B can operate properly.

Each of the electric power supply monitoring sections 7 is so designedas to transmit the value of a power source voltage to the respectivesensor signal transmitting section 9A or 9B and the sensor signalreceiving section 13 may be so designed as to check to see whether thesupplied electric power is normal or abnormal. If a normal indicationsignal is transmitted when the power source voltage is normal, buttransmission of the normal indication signal is interrupted when thepower source voltage is abnormal, it is possible to monitor the lack ofthe supplied electric power and the presence or absence of anabnormality in each of the sensor signal transmitting sections 9A and9B.

The lowest voltage at which each of the electric power supply monitoringsections 7 operates normally is preferably lower than the lowest voltagerequired for the sensor sections 6A and 6B and the sensor signaltransmitting sections 9A and 9B to operate normally. Where the electricpower supply units 10 are provided with respective capacitors orsecondary batteries, the electric power available therefrom may be usedto power the electric power supply monitoring sections 7.

The sensor signal receiving unit 5 is preferably provided with a monitordependent electric power control section 14 to increase the electricpower to be transmitted from the feed power transmitting section 12,when the electric power source voltage attains a value lower than athreshold value (or not higher than a threshold value), and to restoreit back to a normal value when the electric power source voltage exceeds(or is not lower than) a threshold value. The threshold value at whichthe electric power to be transmitted is restored to the normal value maybe set to a value lower than a threshold value at which the electricpower to be transmitted is increased. In this way, frequent switching ofthe electric power can be avoided.

The sensor signal receiving unit 5 or the like may be provided with anabnormal time processing means 15 operable, when the electric power tobe supplied does not restore even though the electric power to betransmitted is increased as a result of the electric power sourcevoltage lowering to a value equal to or lower than the threshold value,to perform a predetermined processing for abnormality until it isrestored.

Also, an abnormality indicating means 16 may be provided, which isoperable to determine that one or both of the wireless sensor units 4Band 4B fail to operate properly, when the electric power to be supplieddoes not restore even after passage of a predetermined length of timesubsequent to the increase of the electric power to be transmitted.

According to the wireless sensor system of the above describedconstruction, since the feed voltage of each of the electric powersupply sections 10 for transmitting an electric driving power to thecorresponding sensor section 6A or 6B and the sensor signal transmittingsection 9A or 9B is monitored by the associated electric power supplymonitoring section 7, an indication of a failure of the electric powersupply is effective to avoid an erroneous operation of the sensorsection 6A or 6B and an erroneous operation of the wireless sensorsystem as a whole. Also, since the electric driving power of therespective electric power supply section 10 is monitored, a troubleoccurring in the electric power source in the associated sensor section6A or 6B and that in the associated sensor signal transmitting section9A or 9B both resulting from failure to supply the electric power can bedetected and, therefore, a simplified structure can be tailored ascompared with the separate and additional use of an abnormalitydetecting means. Yet, if depending on the result of monitoring, acontrol is made to increase the electric power to be transmitted in theevent of the power supply failure, there is no need to transmit a highelectric power at all times and, therefore, the electric powerconsumption of the wireless sensor system can be reduced.

FIG. 13 illustrates a different application of the wireless sensorsystem according to the first embodiment to the wheel support bearingassembly. The wheel support bearing assembly 33 shown therein includesan outer member 1 having a plurality of raceways, an inner member 2having raceways defined in face-to-face relation with the racewaysreferred to above, and two rows of rolling elements 3 interposed betweenthe mutually confronting raceways and is used to rotatably support avehicle wheel relative to a vehicle body. The wheel support bearingassembly 33 shown therein is of a fourth generation type, in which theinner member 2 is made up of a hub axle 2A and an outer race 15 a of theconstant velocity universal joint 15, with the raceways in the innermember 2 being defined in the hub axle 2A and the outer race 15 a of theconstant velocity universal joint 15, respectively.

The single wireless sensor unit 4A is mounted on the outer member 1 ofthe wheel support bearing assembly 33. The other wireless sensor unit 4Bshown in FIG. 1 may be dispensed with or may be disposed separate fromthe wheel support bearing assembly 33 and in the vehicle wheel fordetection of, for example, the tire pressure.

The wireless sensor unit 4A includes a revolution sensor 6Aa as a sensorforming a part of the sensor section 6A. This revolution sensor 6Aa ismade up of a pulsar ring 17 a and a magnetic sensor 18 a disposed inface-to-face relation with the pulsar ring 17 a. The pulsar ring 17 ahas a cyclical change in a direction circumferentially thereof such as amagnet magnetized to a plurality of magnetic poles in a directioncircumferentially thereof, or a magnetic ring having defined thereinserrations similar in shape to gear teeth. The magnetic sensor 18 a,when detecting a cyclical magnetic change in the circumferentialdirection of the pulsar ring 17 a, detects a revolution of the innermember 2 relative to the outer member 1 and subsequently outputs arevolution signal. This revolution signal is in the form of a train ofpulses. The magnetic sensor 18 a is a magnetic field sensor and, otherthan the magnetic reluctance type sensor (generally referred to as “MRsensor”), an active type magnetic field sensor such as, for example, aHall type sensor, a flux gate type magnetic field sensor or an MR sensorcan be employed. The magnetic sensor 18 a may be disposed at twolocations spaced about 90° in phase relative to the cycle of magneticchange in a direction circumferentially of the pulsar ring 17 so thatrevolution signals having a phase offset about 90° from each other canbe transmitted. With those two revolutions signals, it is possible todetect the direction of revolution of the vehicle wheel.

The wireless sensor unit 4A forms an integrated unit, in which a circuitbox 24 and a sensor mount 23 are integrated together, and the circuitbox 24 is mounted externally on the outer member 1. The sensor mount 23is accommodated within an annular bearing space delimited between theouter member 1 and the inner member 2 through a radial hole defined inthe outer member 1 so as to extend radially thereof. A communicationfunctional section, comprised of the electric power receiving section 8Aand the sensor signal transmitting section 9A, both shown in FIG. 1, theelectric power supply section 10 and the electric power supplymonitoring section 7 are provided within the circuit box 24, and themagnetic sensor 18 referred to above is arranged in the sensor mount 23.As the other sensor forming the sensor section 6A, a sensor 22 fordetecting information other than the revolutions is disposed in thesensor mount 23. This sensor 22 may be a temperature sensor, a vibrationsensor, a load sensor, a preload sensor or the like.

The sensor signal receiving unit 5 is fitted to the vehicle body. Forexample, it may be fitted inside a tire housing of the vehicle body. Thesensor signal received by the sensor signal receiving unit 5 is suppliedto an electric control unit (ECU) secured to the vehicle body forcontrolling the entire electric control system of the automotive vehicleand is used for various control and abnormality monitoring.

Since the revolution sensor 6Aa includes a pulsar ring 17 a and amagnetic sensor 18 a cooperable with the pulsar ring 17 a to detect therevolution and is supplied an electric power by wireless and, therefore,it can detect the revolution until a zero speed, it can be used with ananti-skid brake system and/or a traction control. By detecting thedirection of revolution, it can be used for a hill hold control, forexample, a control corresponding to detection of rearward movement ofthe automotive vehicle during ascending run or the reverse.

With the other sensor 22 such as, for example, a load sensor or atemperature sensor, a parameter other than the revolution can bedetected and, therefore, the bearing assembly can be designed to befunctionally intelligent, allowing it to be used for the self-diagnosisof the bearing assembly and also for the various automatic controls.

The electric power supply monitoring section 7 monitors the electricpower being supplied, by measuring the value of the electric powersource voltage. A monitor dependent electric power control section 14 isoperable to increase the electric power to be transmitted from the feedpower transmitting section 12, when the electric power source voltageattains a value lower than a threshold value (or not higher than athreshold value), and to restore it back to a normal value when theelectric power source voltage exceeds (or is not lower than) a thresholdvalue. In the event that the electric power to be supplied does notrestore to the normal value even though the electric power to betransmitted is increased, an abnormal time processing means 15 performsa predetermined abnormality processing until it is restored. By way ofexample, in the anti-skid brake system, the anti-skid brakingfunctionality thereof is halted so that the normal braking operation canbe performed.

Also, in the event that the electric power to be supplied does notrestore even after passage of a predetermined length of time subsequentto the increase of the electric power to be transmitted, an abnormalityindicating means 16 determines and then indicates that one or both ofthe wireless sensor units 4B and 4B fail to operate properly.

As hereinabove described, it is possible to avoid any erroneousoperation of the sensor section 6A when the electric power to besupplied is monitored through measurement of the electric power sourcevoltage and the presence of an abnormality in the electric power beingsupplied is indicated. Also, by allowing a signal indicative of theelectric power being supplied to be transmitted, the electric power tobe transmitted for the electric power supply can be controlled and,therefore, there is no need to transmit the large electric power at alltimes, allowing the electric power consumption of the wireless sensorsystem to be reduced. This leads to increase of the mileage.

FIG. 14 illustrates an example, in which this wireless sensor system isapplied to a different type of the wheel support bearing assembly 33.This wheel support bearing assembly 33 is of a third generation type, inwhich the inner member 2 is made up of a hub axle 2A and an inner racesegment 2B mounted externally on one end of the hub axle 2A and racewaysin the inner member 2 for the respective rows of the rolling elementsare defined in the hub axle 2A and the inner race segment 2B,respectively. The constant velocity universal joint 15 has a shaftportion provided in an outer race 15 a thereof and inserted into the hubaxle 2A and is then coupled thereto by means of a nut.

The wireless sensor unit 4A is mounted on an end of the outer member 1.The sensor section 6A of the wireless sensor unit 4A is in the form of arevolution sensor 6Aa including a pulsar ring 17, mounted on the innermember 2, and a magnetic sensor 18 disposed in face-to-face relationwith the pulsar ring 17. The pulsar ring 17 in turn includes amultipolar magnet or the like. The pulsar ring 17 is arranged on acomponent part of the sealing member used to seal the annular bearingspace delimited between the outer member 1 and the inner member 2. Themagnetic sensor 18 is employed in the form of a magnetic reluctancesensor or a Hall element sensor. Other structural features thereof aresimilar to those in the example shown in FIG. 3.

FIG. 15 illustrates a different case in which this wireless sensorsystem is applied to a further different wheel support bearing assembly33. This wheel support bearing assembly 33 is of a third generation typefor supporting an vehicle driven wheel. In this example, the wirelesssensor unit 4A is secured to a cover 25 for covering one end of thebearing assembly. The wireless sensor unit 4A makes use of, as thesensor section 6A, a revolution sensor 6Aa made up of a pulsar ring 17 aand a magnetic sensor 18 a. The sensor section 6A including the magneticsensor 18 a has its free end inserted into a hole defined in the cover25 and a circuit box 24 is arranged on an outer surface of the cover 25.Other structural features of this embodiment are similar to those in theexample shown in FIG. 14. It is to be noted that the inner race segment2B is fixedly coupled with the hub axle 2A by means of a crimped portion100 formed by crimping one end of the hub axle 2A.

FIG. 16 illustrates the wireless sensor unit according to a fourthpreferred embodiment of the present invention. This wireless sensorsystem makes use of the wireless sensor unit 4A including, as the sensorsection 6A thereof, a revolution sensor 6Ab having an electric powergenerating capability, and the electric power supply section 10 utilizesan electric power generated by the revolution sensor 6Ab. In thisfigure, the use is shown of another sensor section 6Ac separate from thesensor section 6Ab serving as an electric power generator, but thesensor may be of a type including only the revolution sensor of anelectric power generating type. It is to be noted that the electricpower supply section 10 may include an electric power receiving section8A, as shown by the broken line in FIG. 16, which utilizes both of anelectric power generated by the revolution sensor 6Ab and an electricpower received by the electric power receiving section 8A. The electricpower supply section 10 has a capacitor 27. The electric power supplymonitoring section 7 is rendered to monitor the feed power voltage ofthis electric power supply section 10. Other structural feature of thisembodiment are similar to those in the embodiment shown in FIG. 1.

As hereinbefore described, even where the electric power generated bythe revolution sensor 6Ab is utilized, the provision of the electricpower supply monitoring section 7 for monitoring the voltage of theelectric power supply section 10 of the wireless sensor unit 4A allowsboth of an abnormal electric power of the sensor sections 6Ab and 6Acand an abnormality occurring in the electric power supply of the sensorsignal transmitting section 9A, to be detected and, therefore, ascompared with the separate use of abnormality detecting means, thestructure can be simplified.

FIG. 17 illustrates an example of the wheel support bearing assembly 33utilizing the revolution sensor 6Ab of the electric power generatingtype in the wireless sensor unit 4A. This wheel support bearing assembly33 is of a type, in which in the third generation type shown in FIG. 14,the revolution sensor 6Ab used therein is employed in the form of anelectric power generating type. The pulsar ring 17 a of the revolutionsensor 6Ab is a multipolar magnet type as shown in FIG. 14, and themagnetic sensor 18 a is comprised of a coil and a core so that rotationof the pulsar ring 17 a relative to the magnetic sensor 18 a can resultin generation of an electric power. Other structural feature of thisembodiment are similar to those in the example shown in FIG. 14.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings which are used only for the purpose ofillustration, those skilled in the art will readily conceive numerouschanges and modifications within the framework of obviousness upon thereading of the specification herein presented of the present invention.Accordingly, such changes and modifications are, unless they depart fromthe scope of the present invention as delivered from the claims annexedhereto, to be construed as included therein.

1. A wireless sensor system, comprising: one or a plurality of wirelesssensor units including a sensor section to detect a detection object, asensor signal transmitting section to transmit wirelessly a sensorsignal outputted from the sensor section, and an electric power supplysection to supply an electric driving power to the sensor section andthe sensor signal transmitting section; a sensor signal receiving unitto receive the sensor signal transmitted from the sensor signaltransmitting section; an electric power supply monitoring section tomonitor a voltage of the electric power supply section; an electricpower receiving section provided in the electric power supply section toreceive an electric driving power transmitted wirelessly from a feedpower transmitting section; and a monitor dependent control section toregulate an electric power to be transmitted from the feed powertransmitting section, in dependence on a monitored result information.2. The wireless sensor system as claimed in claim 1, wherein the feedpower transmitting section is provided in the sensor signal receivingunit.
 3. The wireless sensor system as claimed in claim 1, wherein theelectric power supply monitoring section monitors the voltage after theelectric power received by the electric power receiving section has beenconverted into a direct current.
 4. The wireless sensor system asclaimed in claim 1, wherein the sensor signal transmitting sectiontransmits a predetermined normal indication signal when the voltagemonitored by the electric power supply monitoring section is equal to orhigher than, or exceeds, a predetermined threshold value, and interruptsthe transmission of the normal indication signal when such voltage islower than, or equal to or lower than, the predetermined thresholdvalue.
 5. The wireless sensor system as claimed in claim 1, wherein thesensor section includes a revolution sensor having an electric powergenerating function, and wherein the electric power supply sectionutilizes an electric power generated by the revolution sensor.
 6. Thewireless sensor system as claimed in claim 1, wherein the sensor sectionincludes at least one of a vibration sensor, a temperature sensor, aload sensor, a torque sensor, and a preload sensor to detect a preloadof a bearing assembly.
 7. The wireless sensor system as claimed in claim1, wherein the sensor section is provided in a plural number.
 8. Thewireless sensor system as claimed in claim 1, wherein there is provideda plurality of wireless sensor units, each of the wireless sensor unitsincluding the sensor section, the sensor signal transmitting section andthe electric power receiving section.
 9. The wireless sensor system asclaimed in claim 1, wherein there is provided one wireless sensor unitincluding a plurality of the sensor sections, the sensor signaltransmitting section and the electric power receiving section, andwherein the sensor signal transmitting section transmits respectivesensor signals from the plural sensor sections.
 10. The wireless sensorsystem as claimed in claim 1, wherein the sensor section is arranged ina bearing assembly.
 11. The wireless sensor system as claimed in claim1, wherein a plurality of wireless sensor units are arranged indifferent bearing assemblies in a machine setup.
 12. A wireless sensorequipped bearing assembly comprising: a bearing assembly; and thewireless sensor system as claimed in claim 1, including the sensorsection, the sensor signal transmitting section, and the electric powerreceiving section to receive wirelessly an electric operating power forthe sensor section and the sensor signal transmitting section, allprovided in the bearing assembly, wherein the sensor section includes atleast one of a vibration sensor to detect a vibration of the bearingassembly, a temperature sensor to detect a temperature of the bearingassembly, a load sensor to detect a load acting on the bearing assembly,a torque sensor to detect a torque acting on the bearing assembly, and apreload sensor to detect a preload of the bearing assembly.
 13. Awireless sensor equipped wheel support bearing assembly to rotatablysupport a vehicle wheel relative to a vehicle body, comprising: an outermember having a plurality of raceways; an inner member having racewaysdefined in face-to-face relation to the raceways; and a plurality ofrows of rolling elements interposed between the mutually confrontingraceways, wherein the wheel support bearing assembly comprises thebearing assembly as defined in claim
 12. 14. A wireless sensor equippedbearing assembly, wherein the wireless sensor unit in the wirelesssensor system as claimed in claim 1 is employed in the bearing assembly.15. A wireless sensor equipped wheel support bearing assembly torotatably support a vehicle wheel relative to a vehicle body,comprising: an outer member having a plurality of raceways; an innermember having raceways defined in face-to-face relation to the raceways;and a plurality of rows of rolling elements interposed between themutually confronting raceways, wherein the wheel support bearingassembly comprises the wireless sensor unit in the wireless sensorsystem as claimed in claim
 1. 16. The wireless sensor equipped wheelsupport bearing assembly as claimed in claim 15, wherein the sensorsection in the wireless sensor unit includes a revolution sensor fordetecting a relative revolution of the outer member to the inner member.17. The wireless sensor system as claimed in claim 1, wherein theelectric power supply monitoring section transmits a monitored resultinformation from the sensor signal transmitting section in the wirelesssensor unit to the sensor signal receiving unit.